In recent years, the size and viewing angle of display devices have increased, and the display of more realistic images than conventional ones is becoming available. In a conventional display device, however, an image is forcibly perceived as being located on the display surface of the display device, and there is a risk of stereoscopic feeling being hindered from being generated by sensory stereoscopic elements such as shadows and composition. This is considered to be affected by influences caused by physiological stereoscopic elements, such as changes in the angle of convergence caused when the display surface of the display device is viewed with two eyes and the occurrence of distortion induced by binocular disparity.
A known optical device for removing such influences caused by physiological stereoscopic elements is a stereoscope called synopter. The synopter is designed to be used with a half mirror to individually supply light received at the same position to two eyes. It is known that this synopter allows retinal images of the two eyes to be identical to each other so that stereoscopic depth can be added to a non-stereo image (see, for example, Non-Patent Document 1).